Iron-based particles have long been used as a base material in the manufacture of structural components by powder metallurgical methods. The iron-based particles are first molded in a die under high pressures to produce a desired shape. After the molding step, the compacted or “green” component usually undergoes a sintering step to impart the necessary strength to the component.
The strength of compacted and sintered components can be increased by the addition of certain metallurgical additives, e.g., alloying elements, usually in powder form. Similarly, the machinability of sintered parts, and consequently tool durability, can be improved with the addition of metallurgical additives.
Unfortunately, metallurgical additives may also impart undesired properties to metallurgical compositions. For example, manufacturers sometimes desire to limit the amount of copper and/or nickel used in compacted metallurgical parts due to the environmental and/or recycling regulations that control the use or disposal of those parts.
Addition of metallurgical additives should not impair a compacted part's mechanical properties, such as for example, ductility, or compressibility. For example, copper and nickel-containing powder metallurgy parts often suffer from low ductility and thus pose certain design constraints when selecting metallurgical additives. Similarly, manganese sulfide often lowers the compressibility of metallurgical powders due to its low density.
A compacted part's dimensional stability during sintering may also be affected by metallurgical additives that burn out of compositions during sintering. In some applications, for example, additions of sulfur have been shown to reduce the ultimate tensile strength and elongation and increase the dimensions of sintered parts.
The cost associated with utilizing metallurgical additives can add up to a significant portion of the overall cost of the powder composition. Therefore, it has always been of interest in the powder metallurgical industry to try to develop less costly metallurgical additives to reduce and/or replace entirely commonly used alloying elements. Accordingly, there exists a current and long felt need in the powder metallurgical industry to develop alternatives to the use of, or decrease the amount of, various common metallurgical additives in metallurgical powder compositions.